Sending queue keeps getting stuck

I have a long sending queue, and it doesn’t help that every couple of hours the queue seemingly gets stuck.
I assume it gets stuck (officially the queue webpage still runs) because suddenly the active list of campaigns has the message counter frozen.
As soon as I hit refresh in the queue’s webpage, the counter starts working again.

  1. How do I know if it’s really stuck or not?
  2. If it’s really stuck, why doesn’t it just tells me there’s a problem?
  3. If it’s really stuck, how come refreshing helps?
  4. Could this be related to following the steps from Limit the messages per hour ?